Geologies of Different Planetary Bodies

I'm fascinated with the different climates and geologies that are possible in other areas of our solar system, so I wanted to share them with the world. Please feel free to make requests for different places!

[climates-in-space]

Enceladus

We are now taking a trip to lovely Saturn! Enceladus is one of her more interesting moons. Unfortunately, it is nowhere near Europa levels of interesting, but it does have a very active interior for being a tiny icy rock. Turns out, the interior is so active that it has a constantly erupting volcano! Now, like Pluto, this volcano is not made of molten rock - it’s far too cold in the outer solar system for that. This one is made of water, originating from the liquid ocean that lies under its icy crust (much like Europa).

This plume of water is actually strong enough that it leaves Enceladus and goes out into space to begin circling Saturn by itself as small icy particles. These particles gradually accumulate over time to create one of Saturn’s famed rings! That’s right; this moon is giving itself up so Saturn can continue to mystify us with her beauty.

Rings actually aren’t that uncommon; Jupiter, Uranus, and Neptune all have them (with Uranus’s being the next largest). However, Saturn’s rings are massive, and probably were formed from one of its moons getting a bit too close and then being sucked in and ripped apart. The rocky part of the moon then went into Saturn while the icy parts flew out to circle Saturn independently. 

These rings are slowly disappearing, though; ice particles run into each other and accumulate over time to create little mini-moons. Other particles are being lost to space, larger moons, and Saturn itself. Therefore, we should thank Enceladus for doing the opposite and giving itself up so Saturn may remain beautiful for a while longer.

If you want to learn more about how they discovered Enceladus’s plume, check out this article: https://science.sciencemag.org/content/311/5766/1422

tl;dr - Enceladus is one of Saturn’s moons and it is constantly erupting water to create another ring around the gas giant.

[climates-in-space]

Venus

Venus started out just like Earth, but now it is incredibly hot with a thick, noxious atmosphere. How does that work? Will Earth do that?? Are we turning Earth into a Venus through global warming and greenhouse gases?!?

Ok probably not. Venus is closer to the Sun than Earth is, which warmed the planet initially to the point where all its water evaporated and went into the atmosphere. We’ll all be dead before Earth gets that hot, and it will probably be because the Sun is going to expand in the next few billion years, not due to our actions (not saying climate change is not a problem, just not a Venus-level problem).

Water is actually the most potent greenhouse gas, but Earth has a cycle that keeps it from collecting in the atmosphere; on the other hand, Venus was close enough that all its water evaporated and heated the planet up considerably. At that point, the water molecules were so hot they were breaking apart and the hydrogen was going into space, while carbon, sulfur, nitrogen, and other heavy elements gained enough energy to go into the atmosphere and bind with the leftover oxygen. This resulted in an extremely dense atmosphere, with about 90 atms of pressure on the surface - that is the same pressure as if you were 900 meters deep in the ocean!

On top of all the pressure and density, the atmosphere is primarily comprised of carbon dioxide, with sulfuric acid clouds and haze. These gasses give Venus an extreme greenhouse effect, so that on its surface, lead would melt. Suffice to say, it is an extremely barren and hostile environment, considering it’s named after the Roman goddess of love.

You can learn more from NASA, as always, or from this article about the atmospheric composition: https://www.sciencedirect.com/science/article/pii/001910358290080X

If you’re really into chemistry, this article is more recent and talks about how Venus is the first place we’ve been able to find energetic neutral atoms. (Most energetic atoms turn into ions): https://www.sciencedirect.com/science/article/pii/S0032063307003819

tl;dr - Venus is hot enough to melt lead on its surface because its atmosphere is extremely dense and toxic. It’s made of mostly carbon dioxide and lots of sulfuric acid clouds, even though it started out (at the beginning of the solar system) just like Earth. 

[climates-in-space]

Jupiter

Jupiter is an incredible planet, massive enough to have played a large role in the formation of our solar system and the order of the planets. It is made of mostly hydrogen and helium, just like the sun. In fact, if there had been more mass available when the solar system was forming, it may have turned into a star, but because the sun was consuming most of the mass already, it didn’t have enough. To become a star, an astrological body would need enough mass to start nuclear fusion of hydrogen (the center would have to be so dense that the hydrogen atoms would spontaneously collide and turn into helium). Jupiter doesn’t come close to that, but it is large enough to create other things with hydrogen. 

Jupiter has a layer of hydrogen that is so dense it turned into a metal. That requires an insane amount of pressure, to cause a gas to become metallic, like iron. Speaking of iron, that is the metal that Earth has at its core that gives it a magnetic field. Jupiter has a magnetic field, too, but it’s because of hydrogen! This metallic hydrogen is still in liquid form, because it also becomes incredibly hot when the pressure gets that intense - around 24000 degrees C or 46000 degrees F. Even if it’s not intense enough to fuse hydrogen, it is a crazy environment, nonetheless.

You can learn more from NASA or scientific articles like this one that talks about how the metallic hydrogen layer works: http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1975ApJ...200L.119S&db_key=AST&page_ind=0&data_type=GIF&type=SCREEN_VIEW&classic=YES

tl;dr - Jupiter is so dense that its hydrogen turns into a liquid metal and gives it a magnetic field. 

[climates-in-space]

Pluto

Poor Pluto, the rejected planet. Interestingly enough, it was downgraded to a dwarf planet not because of its size (which is fairly arbitrary), but because its orbit is extremely elliptical, while all of the other planets’ orbits are more circular. However, that is not why we are investigating Pluto.

Pluto happens to be right at the triple point of N2. (Triple point is where the substance can exist as either a solid, liquid, or gas. Earth is at the triple point of water, which is why water is common in all its states.) That means Pluto has interesting N2 formations. 

For reference, N2 is a common nitrogen molecule that makes up over 70% of Earth’s atmosphere. It is the substance that makes up super cold liquid nitrogen. Since it’s that hard to create liquid nitrogen on Earth, imagine how cold Pluto must be to have large quantities of nitrogen ice! Water ice is also very common on Pluto.

In fact, there is a huge nitrogen ice sheet called the Sputnik Planitia (that big white section on the picture above) that has lots of different terrains on it; plains, pits, troughs, and erosion from glacier flows. These glaciers have moved around and eroded mountains on Pluto. These mountains are not made of rock, though; they are made of water!

These nitrogen glaciers and plains go through cycles as Pluto gets further and closer to the sun (again, because its orbit is so elliptical, it ends up getting what are effectively seasons). This affects the movement and state changes of the nitrogen glaciers. There actually aren’t any liquid nitrogen rivers on Pluto because its surface pressure is almost nonexistent (it doesn’t have an atmosphere), but the glaciers move similarly to rivers and end up carrying other types of ices across Pluto’s surface. In this way, nitrogen acts a lot like water does on Earth.

You can learn more from NASA or scientific articles like this one that goes in depth about Sputnik Planitia and how it changes over time: https://www.sciencedirect.com/science/article/abs/pii/S0019103517306966

tl;dr - Pluto is so cold it has layers of nitrogen ice that are often in glaciers and plains. These move and change over time because Pluto’s super elliptical orbit gives it effective ‘seasons’. 

[climates-in-space]

Europa

Europa is a moon of Jupiter, and it is really interesting because it is very likely to host life! It has an ocean with hot volcanic vents bubbling into it, giving the surrounding water energy. Fun fact: Earth also has lots of volcanic vents in our ocean, and they’re full of life! They may have even been where life began on Earth.

(Above picture shows some of the life that surrounds these underwater volcanic vents on Earth.)

Europa is farther out than Mars; how can it be warm enough to do support life? The answer is that it is in a weird orbital pattern with two of Jupiter’s other moons, Ganymede and Callipso so that their gravitational pulls tug on each other. These forces compress and expand its rocky interior, giving it lots of energy to be tectonically active enough to create those vents.

Now, what about its ocean? How do we know that exists when everything is covered in ice? Europa actually has a lot of cracks in its top ice crust. This shows that there is a liquid layer moving underneath its surface, and given Europa’s density, it is probably liquid water. Water and rock can easily react to form simple organic molecules (like basic carbohydrates and parts of amino acids) very easily; these molecules are often found on meteorites, having formed in space. Because of this, single-celled organisms may have developed in Europa (or other organisms in forms we haven’t seen yet)!

To learn more, visit NASA’s website, or check out this scientific article all about Europa’s cracks: http://science.sciencemag.org/content/285/5435/1899

tl;dr - Europa (moon of Jupiter) may be able to support life because it has volcanic vents at the bottom of its ocean.